Continuous opacity reading - Wetscrubber

[ChemEnv8]

We plan to install two new boilers fired with biomass. In order to get the permit, we must install a continuous opacity monitoring system (COMS). But the thing is that our gaz pass through a cyclone and a wetscrubber, and it will be saturated in water. So the precision of the opacity measure can definitely be affected, as each water drop will be read as a PM.

We were thinking of installing a Beta attenuation technology to read PM directly at the stack and calculate opacity but this solution can be expensive.

Another avenue might be, reading opacity before the wetscrubber, and measuring the increase of contaminant in the wetscrubber solution (maybe by absorption?) and determining indirectly what is the opacity at the stack, but we're not sure if that can actually work.

Any idea?

 

[cheute79]

ChemEnv8:

Stack monitoring or emissions verification is always much more challenging than it seems from the outside. I don't know how direct opacity monitoring can possibly work with the high humidity off of biogas. My experience with regulatory agencies (almost all in the USA, but a little in Italy) has been that the regulators or those who write the permit put common, base and usually accepted requirements for monitoring in the permit, and it's your job to negotiate something that actually works. They just want verification.

have you explained to the agency (go direct to the permit writer or the department head or chief, not to the generic agency) what the issues are? This needs to be done in a manner that does not impugne the competance of the person, but explaining in detail the situation. Propose an alternative, and make it look as if it will be more rigorous or dependable than a COMS, like a specific IR (if water does have a similar response), so the agency will be getting more than they might normally expect. This isn't always easy, and will put the workload on you, but in the long run, it's well worth it.

You could look into cooling and condensing the stack gas, but that is usually a huge materials and cost problem. Good luck!